A recent matched cohort study1 published in BMC Medicine found that in a cohort of patients in the UK, SARS-CoV-2 was associated with an increased incidence of psoriasis, among several immune-mediated inflammatory diseases (IMID). Increased incidence was also associated with type 1 diabetes mellitus and inflammatory bowel disease.
Investigators Syed et al sought to explore the relationship between SARS-CoV-2 infection and IMIDs, particularly when comparing incidence of IMIDs in patients with SARS-Cov-2 infection versus those without a history of infection.
The retrospective cohort study began with data extraction from the Clinical Practice Research Datalink Aurum with all data between January 31, 2020, and June 30, 2021. Patients included in the study were all above the age of 18 at baseline and who were registered with a general practice for at least 12 months prior to inclusion. All participants had an acceptable patient flag and a lack of prior history of IMIDs in the primary outcome.
- A matched cohort study in the UK found that SARS-CoV-2 infection was associated with an increased incidence of immune-mediated inflammatory diseases (IMIDs), including psoriasis, type 1 diabetes mellitus, and inflammatory bowel disease.
- Psoriasis accounted for more than 30% of all new IMID diagnoses and was approximately 23% more likely to occur in patients with SARS-CoV-2 exposure compared to those without exposure.
- The study suggests that a subgroup of long COVID may be linked to immune-mediated inflammatory mechanisms, supporting this hypothesis. However, the study had limitations related to missing data and potential misclassification of exposure status.
Patients were then stratified into either a group with a history of SARS-CoV-2 exposure or a group with a lack of exposure history. All patients with a prior diagnosis (n=458,147) were matched with patients with a lack of confirmed diagnosis or who had a prior suspected diagnosis (n=1,818,929).
Researchers then explored the incidence of various IMIDs, including:
- Autoimmune thyroiditis
- Celiac disease
- Inflammatory bowel disease
- Myasthenia gravis
- Pernicious anemia
- Rheumatoid arthritis
- Sjogren syndrome
- Systemic lupus erythromatosus
- Type 1 diabetes mellitus
Of these IMIDs, SARS-CoV-2 infection was significantly associated with an increased incidence of psoriasis, type 1 diabetes mellitus, and inflammatory bowel disease. Psoriasis, which represented more than 30% of all new IMID diagnoses among both cohorts and was the second most diagnosed IMID, was approximately 23% more likely to occur in patients of the exposed cohort as opposed to the unexposed cohort.
“The relatively high incidence of psoriasis in the SARS-CoV-2 infected cohort is supported by other reports from the literature which found increased cases of psoriasis, and flares of existing disease, following COVID-19,” study authors Syed et al wrote.
Potential study limitations included missing sufficient data for ethnicity, body mass index, smoking status, and socioeconomic status. Additionally, the length of study period, follow-up period, and potential for misclassification of exposure status were considered limitations of the study.
“SARS-CoV-2 infection was associated with a 22% relative increase in the risk of developing certain immune-mediated inflammatory diseases, including type 1 diabetes mellitus, inflammatory bowel disease, and psoriasis,” wrote study authors. “These findings support the hypothesis that a subgroup of long COVID may be caused by immune-mediated inflammatory mechanisms.”
- Syed U, Subramanian A, Wraith DC, et al. Incidence of immune-mediated inflammatory diseases following COVID-19: a matched cohort study in UK primary care. BMC Med. 2023;21(1):363. Published 2023 Sep 21. doi:10.1186/s12916-023-03049-5